Looking closely at the frame, it appears to be a 73 VR or 74
Enduro frame. These two models had the one piece front motor
mount. (later models used the alloy plate attachment) I also see
the airbox mounts on the frame, which consisted of two bolts on
either side, which mounted a small "bath tub" style airbox, that
could easily fit between the added frame stiffners.
It does appear that some extra metal has been added to beef
up the motor mounts.